160 THE CHICAGO ACADEMY OF SCIENCES. 
pressed; whorls five and one-half to six, rounded, convex, 
rather closely coiled; spire elevated, obtusely conical; aperture 
forming a triangle with rounded base, contracted behind the 
peristome, which is thickened, roundly reflected, white, with a 
small callosity near the umbilical region; the upper part of the 
peristome is more reflected than the rest, so that ina front view 
of the aperture this part presentsa thin edge instead of a broad 
curved surface; terminations widely separated, connected bya 
very thin callus; umbilicus closed but the region indented; base 
flatly rounded. 
Greater diameter, 18.50; lesser, 15.50; height, 12.00 mill. (12395.) 
as us POs tO BL 002 18005 fs a3s05)) 
Fic. 24. 
Radula of PoLYGYRA PENNSYLVANICA Green. (Original.) c, cen- 
tral tooth; 1, first lateral; 9, second marginal; 16, 18, ninth and eleventh 
marginals; 25, eighteenth marginal; J, jaw. 
Animal: With a long and narrow foot, 27.50 mill. long 
and 4 mill. wide; color blackish or lead color on head, neck 
and eye-peduncles lighter on base of foot; heart situated near 
junction of peristome with body-wall; pulsations regular, 
eighty-five per minute. / 
Jaw: Arched, ends squarely truncated; anterior surface 
armed with eleven wide, heavy ribs which denticulate the upper 
and lower margins. The jawis of the same width throughout 
its length (Fig. 24, J). 
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